82-27-08 Forward Fin Spar S/N 38-78A0001 thru 38-82A0122.
To prevent possible failure of the fin and associated fuselage structure because of fatigue damage.
(a) On S/N 38-78A0001 through 38-80A0198
(1) On airplanes which do not have Kit P/N 764427 on an undamaged forward fin spar.
Before 325 hours and then at intervals not over 100 hours thereafter.
(i) Inspect the forward surface of the forward fin spar web P/N 77601-03 in the area of the forward fin spar
attach fitting P/N 77553-05 for cracks using a dye penetrant method. Remove two forward fin attach bolts
and displace fin spar 1/8" laterally in each direction to increase visibility of spar area adjacent to
edge of attach fitting. Remove any scuff marks on spar by burnishing prior to applying dye penetrant.
(ii) Replace or repair forward fin spars having cracks exceeding 1/2" long with forward fin spar
P/N 77601-1 and Forward Fin Spar Modification Kit 764427. Replace or repair parts which have cracks less
than one-half inch within 25 hours.
(2) On airplanes without fuselage bulkhead assembly P/N 77553-06.
Before 325 hours and then at intervals not over 300 hours thereafter.
(i) Inspect the fuselage bulkhead assembly P/N 77553-02 at fuselage station 221.42, in the area of the
Forward Fin Spar Attach Plate P/N 77553-05, for cracks using a dye penetrant method or equivalent.
Access the aft side of the bulkhead by removing rudder and adjacent access door and to front side by
removing the luggage compartment rear partition. When using luggage compartment, provide a stand to
support the aft fuselage and provide a support board for the mechanic.
(ii) Repair or replace bulkheads having cracks exceeding 3/4" long with bulkhead assembly P/N 77553-06,
or equivalent part. Replace or repair parts which have cracks less than 3/4" long within 25 hours.
(3) On airplanes without Aft Vertical Fin Spar Assembly P/N 77601-16, Upper Rudder Hinge Shim P/N 85606-02,
and Fuselage Bulkhead Assembly P/N 85615-02, before 2500 hours and every 200 hours thereafter,
(i) Inspect Aft Vertical Fin Spar P/N 77601-02 for cracks as per SB 745, Part IV, by dye penetrant method or equal.
(ii) If cracked, repair or replace Aft Fin Spar P/N 77601-02 and Aft Fuselage Bulkhead Assembly P/N 77554-02,
with Aft Vertical Fin Spar Assembly P/N 77601-16, Upper Rudder Hinge Shim P/N 85606-02, and
Fuselage Bulkhead Assembly P/N 85615-02.
(4) Within 25 hours or at 3000 hours TT, whichever is later, and thereafter at intervals not over 3000 hours, replace
the Forward Fin Spar Attachment Plate P/N 77553-05 with a new part.
